PoLaK

iTrader: (1)

Charlie this is a vaccume activated valve right....is it possible that it just not opening at 7250 because there isn't as much air moving through the throttle body as if I were truly going 150mph?

Re-evaluating my previous dynograph of the RB parts it does appear that it did open at 7250 not that it made much power by doing it.....

Nathan could we get torque and HP on one larger higher resoultion graph to see if there is indeed a dip at 7250 or at least a zoom in on that area?

zoom44

no its got a solenoid that opens first then the vacuum operates the vdi

VARIABLE DYNAMIC EFFECT INTAKE-AIR (VDI) SOLENOID VALVE INSPECTION

1. Disconnect the negative battery cable.

2. Remove the VDI solenoid valve. (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION.)

3. Inspect for airflow with the steps in the table below.

*

If it is normal, inspect related wiring harnesses.
*

If there is any malfunction, replace the VDI solenoid valve. (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION.)

Circuit Open/Short Inspection

1. Disconnect the PCM connector. (See PCM REMOVAL/INSTALLATION.)

2. Inspect the following wiring harness for open or short (continuity check).

Open circuit

*

If there is no continuity, the circuit is open. Repair or replace the harness.

o

VDI solenoid valve terminal B (harness-side) and PCM terminal 1W

o

VDI solenoid valve terminal A (harness-side) and main relay terminal C (harness-side)

Short circuit

*

If there is continuity, the circuit is shorted. Repair or replace the harness.

o

VDI solenoid valve terminal B (harness-side) and body GND

o

VDI solenoid valve terminal A (harness-side) and power supply

sorry there are pics but i cant post them at the moment

zoom44

vacuum side -

VARIABLE DYNAMIC EFFECT INTAKE-AIR (VDI) ACTUATOR INSPECTION

1. Disconnect the VDI actuator vacuum hose.

2. Install the vacuum pump to the VDI actuator.

3. Verify that the rod moves as indicated in the table below when gradually applying a vacuum to the VDI actuator.

*

If it fails, replace the VDI actuator. (See INTAKE MANIFOLD REMOVAL/INSTALLATION.)

Rod movement

Vacuum

(kPa {mmHg, inHg})


Rod movement

–3.6 {–27.0, –1.1} or more


Starts to move

–27.9 {–209.2, –8.2} or less


Fully pulled

1.2 {9.0, 0.4} or more


Fully returned

Moonrover333

is this a common problem?

TeamRX8

iTrader: (25)

I agree, you should be able to see a slight drop and then ramp up at every intake path change, that's why it's configured that way. Great graph for that purpose

rotarygod

It's strange that the RX-8 shows such dips. On the 6 port 2nd generation RX-7's, you didn't see these dips when the VDI or aux ports opened. At the very least it wasn't nearly as pronounced. For the most part it was quite smooth. I do know that if you bring online another set of injectors at the exact same point as a set of runners is opening that you will get a dip but if you stagger these points by 400-500 rpm, the dip can be smoothened out. This info comes from standalone ecu tuning on an RX-7 but I thought it may be relevant. Obviously it doesn't explain everything on the RX-8 though.

Xyntax

It's my first time on this thread, and since I've seen two charts of my dyno up here and Polak has been asking a fix to this VDI issue, here's my 2 cents:

https://www.rx8club.com/series-i-tech-garage-22/experiment-changing-intake-port-settings-76447/
https://www.rx8club.com/series-i-tech-garage-22/above-3750-rpms-doesnt-open-secondary-ports-light-load-76505/

Read those threads. I'll post a pic of my experiment's setup, so you can get the idea on how to disable VDI. It's just a plug behind the engine that belongs to what I call the "solenoid plug trio". I have skinny long arms than enabled me to reach in touch the top plug, count two plugs down and disconnect.

When you see a dip like that, it doesn't mean the VDI isn't opening. Figure this out, the VDI is closed all the way to 7K RPM right? After that, it opens up. If the VDI is stuck closed, then the chart lines shouldn't show any changes right? So how come, there's a dip? That's because VDI just turned open and disturbed airflow :D

zoom44

right the dip shows a functioning VDI like the mustang dyno plot i linked. flat line plateu at 7250 shows a non functioning VDI. polak's flat lines

evilbada1

hm..when racing beat gutted the entire exhaust system, didn't they only gain close to 8whp or something? how is 20whp gain even possible?

RotaryManiac

RB removed everything(cat and catback), and therefore no back pressure. I think the car needs some back pressure in order to put out max horsepower.

rotarygod

Backpressure does not make power. It never has and it never will at any rpm. You do not need backpressure. I've written in length about this before.

Moonrover333

sooooo does the vdi thing break often? and does it show a CEl when it does or no?

PoLaK

iTrader: (1)

Charlie i took the car out for a drive tonight and the duct seems to be working fine, I'm getting a buzz like change rattling behind the dash everytime I hit 7250 which would seem to indicate that its opening up properally. I really think it might have something to with lack of air flowing though the intake on a dyno that we sometimes get this type of thing.

xzantax interesting stuff did you ever do a proper dyno with the VDI open and VDI closed?

Xyntax

^ If it is lack of airflow, then it should show on my graphs. I have made so many logs on the street and on the dyno. The airflow per RPM is rather consistent in its range. The engine will suck in air regardless of a fan blowing or a freeway run, as long as there is an opening for which air can get through.

No, I haven't dynoed my VDI tests. I'm even thinking of recreating a CZ map for a VDI off setup. I always have a hard time leaning out the 7K RPM range so I end up trimming down too much fuel at that range. With good airflow with the VDI off, my maps will be different this time (I hope). Now, if this rain would just go away for an entire week...

TeamRX8

iTrader: (25)

yeah, and a lot of people will repeat that backpressure BS despite a cat converter being in the system, like it isn't providing any backpressure

classic book/magazine experts ...

crossbow

Its all about exhaust velocity. Backpressure just pops up because people misinterperate the terminology.

Exhaust sizing and design is all about maximizing your exhaust velocity at a certain rpm range.

zoom44

there is a CEL for it stuck open but not closed

brillo

Running no exhaust at all will not make you the most power. If it did, F1/Champcar/Lemans cars would not have exhaust systems as they are not regulated on sound and emissions. Hell, they even use aero dynamic parts to help get the exhaust gases out faster (look at the backs of the cars)

a good free flowing exhaust system (I'm assuming the turboXs qualifies for this) will help in the scavenging process by keeping the velocity high.

Its very possible racing beat, while running the engine on an engine dyno with no exhaust got only 8whp more than with the stock exhaust b/c the stock system with the cat (Racing Beat always takes emissions into account) doesn't flow that well, so removing the whole exhaust system was a semi improvement.

The key is that no exhaust is not the optimal system. (and thank god, this would be loud as all hell)

Red Devil

Thought I'd add to this also as I didn't see it posted before. But Rotary Performance, out of Texas, has claimed for quite some time on their website that with a midpipe and GReddy SP2 they gained 21whp. This seems fairly in line with TurboXS's claims...

http://www.rx7.com/store/rx8/rx8exhaust.html

adrian-1

In your picture below, it has the catless midpipe and the exhaust. Do you have a picture of the rest of the piping that goes with the exhaust? It should be about 4ft in length.

I'm in as soon as I see the gains on a turbo 8.

swoope

iTrader: (5)

to me it looks like a cat back with a resonator...

beers

adrian-1

Nope, I'm positive its their midpipe w/ resonator and exhaust.
But the exhaust is missing another 4ft section, not pictured.

wushunut

I would expect decent gains on a turbo car. I paid them a visit yesterday. Great group of guys and they have a very well run operation going. Nathan is a stand-up guy. He took the time out of his day to talk with me and show me around the shop. He did mention that the exhaust was designed with a turboed car in mind. So I would expect decent results given the results we've seen on the N/A cars thus far. I was really impressed with their knowledge and experience. I think a lot of the problems that WRX owners initially faced with their ECU will translate into good experience for TurboXS when it comes to tuning the 8. Especially since a lot of those same WRX's are running over 400whp! I'm interested in seeing what they will come up with in terms of their Ecutek(sp?) and eventual FI applications. Looks like an exciting development!

turboxs_nathan

You are correct.

Moostafa29